Effect of Interdendritic Separation Defects on Tensile Fracture Properties of Cast Steel

Deterioration of ductility inward the bloom of continuously cast S43C steel associated with small casting defects was studied by tensile test and observation of fractured surface using a scanning electron microscope.Area fraction of the defects in fractured surface Rs, increased with increasing distance from surface to interior of the bloom, and fracture strain εf decreased.Appearance of fracture changed from cup-cone to shear with increase in Rs, and εf decreased linealy with increasing square root of Rs.It was found that these deteriorations were mainly attributed to the increase of small casting defects named intredendritic separation defect resulting from restriction of feeding to compensate the volume contraction in liquid-solid transformation during solidification. This presented a significant effect of the feedability on the ductility of cast steel.